Effects of cassava processing effluents on the soil microbial population dynamics in selected communities in Abakaliki, Ebonyi State, Nigeria

Abstract

Cassava processing effluent constitutes environmental nuisance and pollutes both soil and water which releases foul odour causing air-pollution. This study evaluated the effects of cassava mill effluent on the microbial population dynamics and physicochemical characteristics of soil in selected communities in Abakaliki, Ebonyi State. Soil samples were collected in a depth of 0-20 cm from both cassava mill effluent polluted soil and unpolluted soil samples for three month and conveyed to the laboratory for analysis. The result showed that there was significant difference (p<0.05) in the microbial (bacterial and fungal) population between the polluted and unpolluted sites. Bacterial population ranged from 4.0±0.2x10⁶ Cfu/g to 8.6±0.8x10⁶ Cfu/g, while fungal population ranged from 1.4±0.1 to 3.4 ± 0.3x10⁶ Cfu/g across the three months study period. Most of the bacteria species identified in the polluted and unpolluted sites includes; E. coli, Bacillus species Staphylococcus aureus, Klebsiella pneumonia, Shigella species, Pseudomonas aeroginosa and Proteus species, while fungal species isolated from the polluted site was the Articulospora inflata while the mold, Aspergillus species and the Penicillium species were commonly found in both polluted and unpolluted sites. The physicochemical properties of the soil samples showed that there was no significant difference in the physicochemical characteristics of both polluted and unpolluted sites although the soil physicochemical properties differed very significantly (P<0.001) across the locations studied.  Most of the physicochemical parameters were higher in the polluted soils compared to their unpolluted counterparts except for the exchangeable cations. This study showed that there is a shift in microbial population structure in soils polluted with cassava mill effluent. However, although this increases most physicochemical properties of the contaminated soil such as pH, OC, OM, N and P, it did not lead to significant shift in these parameters in the three months study period across the locations. This study has elucidated the nature of changes in both microbial population structure and physicochemical properties of soil exposed to cassava effluent pollution.